Multi-speed transaxle

ABSTRACT

A front wheel drive transmission is provided having a transmission input member, a transmission output member, four planetary gear sets, a plurality of coupling members and a plurality of torque transmitting devices. Each of the planetary gear sets includes a sun gear member, a planet carrier member, and a ring gear member. The torque transmitting devices include clutches and a brake arranged within a transmission housing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/045,471, filed on Apr. 16, 2008, which is hereby incorporated in itsentirety herein by reference.

FIELD

The invention relates generally to a multiple speed transmission havinga plurality of planetary gear sets and a plurality of torquetransmitting devices and more particularly to a transmission configuredfor a front wheel drive vehicle having eight or more speeds, fourplanetary gear sets and a plurality of torque transmitting devices.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may or may not constitute priorart.

A typical multiple speed transmission uses a combination of a pluralityof torque transmitting mechanisms, planetary gear arrangements and fixedinterconnections to achieve a plurality of gear ratios. The number andphysical arrangement of the planetary gear sets, generally, are dictatedby packaging, cost and desired speed ratios.

While current transmissions achieve their intended purpose, the need fornew and improved transmission configurations which exhibit improvedperformance, especially from the standpoints of efficiency,responsiveness and smoothness and improved packaging, primarily reducedsize and weight, is essentially constant. Accordingly, there is a needfor an improved, cost-effective, compact multiple speed transmission.

SUMMARY

A transaxle is provided having a transmission input member, atransmission output member, a plurality of planetary gear sets, and aplurality of torque-transmitting mechanisms. The plurality of planetarygear sets each have a sun gear member, a planetary carrier member, and aring gear member.

In one aspect of the present invention, the housing of the transaxle hasa first wall, a second wall, and a third wall extending between thefirst and second walls. The first, second, third and fourth planetarygear sets are disposed within the housing. The second planetary gear setis adjacent the first wall, the fourth planetary gear set is adjacentsecond wall, the third planetary gear set is adjacent the secondplanetary gear set and the first planetary gear set is between the thirdand fourth planetary gear sets.

Moreover, the ring gear member of the first planetary gear set ispermanently coupled to the sun gear member of the fourth planetary gearset. The sun gear member of the first planetary gear set is permanentlycoupled to the sun gear member of the second planetary gear set. Theplanet carrier member of the second planetary gear set is permanentlycoupled to the ring gear member of the third planetary gear set. Theplanet carrier member of the third planetary gear set is permanentlycoupled to the planet carrier member of the fourth planetary gear set.The transmission output member is permanently coupled with the carriermembers of the third and fourth planetary gear sets. The transmissioninput member is permanently coupled with the carrier member of the firstplanetary gear set.

Further, the housing has a first area defined radially inward from anouter periphery of the planetary gear sets and axially bounded by thefirst wall and the second planetary gear set, a second area definedradially inward from the outer periphery of the planetary gear sets andaxially bounded by the second and third planetary gear sets, a thirdarea defined radially inward from the outer periphery of the planetarygear sets and axially bounded by the first and third planetary gearsets, a fourth area defined radially inward from the outer periphery ofthe planetary gear sets and axially bounded by the first and fourthplanetary gear set, a fifth area defined radially inward from the outerperiphery of the planetary gear sets and axially bounded by the fourthplanetary gear set and the second wall, and a sixth area definedradially inward from the third wall and radially outward from the outerperiphery of the planetary gear sets and axially bounded by the firstwall and the second wall.

In another aspect of the present invention, a first clutch is disposedin at least one of the second, third, fourth and sixth areas. A secondclutch is disposed in at least one of the third, fourth, fifth and sixthareas. A third clutch is disposed in at least one of the third, fourth,fifth and sixth areas. A first brake is disposed in at least one of thefirst, second and sixth areas. A second brake is disposed in at leastone of the first, second, third and sixth areas. The clutches and thebrakes are selectively engageable to establish at least eight forwardspeed ratios and at least one reverse speed ratio between thetransmission input member and the transmission output member.

In yet another aspect of the present invention, a transfer gear train isprovided having a first and second transfer gear. The first transfergear is rotatably fixed to the transmission output member and the secondtransfer gear is rotatably fixed to an intermediate shaft. Adifferential gear set is provided for driving a pair of road wheels. Apinion gear is rotatably fixed to the intermediate shaft, and an inputdifferential gear in mesh with the pinion gear and configured torotatably drive the differential gear set is also provided.

In still another aspect of the present invention, a power transferassembly having a first and second transfer gear, a power transfermember, a final drive planetary gear set and a differential gear set.The first transfer gear is rotatably fixed to the transmission outputmember and the second transfer gear is rotatably fixed to a drive shaft.The power transfer member is rotatably coupled to the first and secondtransfer gear for transferring rotational energy from the first transfergear to the second transfer gear. The final drive planetary gear set iscoupled to the drive shaft for receiving a driving torque from thesecond transfer gear. The differential gear set is coupled to the finaldrive planetary gear set and to a pair of road wheels for receiving afinal drive rotational torque and transferring the final drive torque tothe pair of road wheels.

Further, areas of applicability will become apparent from thedescription provided herein. It should be understood that thedescription and specific examples are intended for purposes ofillustration only and are not intended to limit the scope of the presentdisclosure.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1A is a schematic diagram of a gear arrangement for a front wheeldrive transmission, according to the principles of the presentinvention;

FIG. 1B is a chart showing the locations of the torque transmittingdevices for the arrangement of planetary gear sets of the transmissionshown in FIG. 1A, in accordance with the embodiments of the presentinvention;

FIG. 2 is a schematic diagram of a front wheel drive transaxlearrangement incorporating the gear arrangement of the transmission ofFIG. 1A and FIG. 1B, according to the principles of the presentinvention; and

FIG. 3 is a schematic diagram of another embodiment of a front wheeldrive transaxle arrangement incorporating the gear arrangement of thetransmission of FIG. 1A and FIG. 1B, according to the principles of thepresent invention.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses.

Referring now to FIG. 1A, an embodiment of a front wheel drivemulti-speed or eight speed transmission is generally indicated byreference number 10. The transmission 10 is illustrated as a front wheeldrive or transverse transmission, though various other types oftransmission configurations may be employed. The transmission 10includes a transmission housing 12, an input shaft or member 14, anoutput shaft or member 16 and a gear arrangement 18. The input member 14is continuously connected to an engine (not shown) or to a turbine of atorque converter (not shown). The output member 16 is continuouslyconnected with a final drive unit (not shown) or transfer case (notshown).

The gear arrangement 18 of transmission 10 includes a first planetarygear set 20, a second planetary gear set 22, a third planetary gear set24, and a fourth planetary gear set 26. The planetary gear sets 20, 22,24 and 26 are connected between the input member 14 and the outputmember 16.

In a preferred embodiment of the present invention, the planetary gearset 20 includes a ring gear member 20A, a planet carrier member 20B thatrotatably supports a set of planet or pinion gears 20D (only one ofwhich is shown) and a sun gear member 20C. The ring gear member 20A isconnected for common rotation with a first shaft or intermediate member42 and a second shaft or intermediate member 44. The planet carriermember 20B is connected for common rotation with input shaft or member14 and a third shaft or intermediate member 46. The sun gear member 20Cis connected for common rotation with a fourth shaft or intermediatemember 48. Each of the pinion gears 20D are configured to intermesh withboth the sun gear member 20C and the ring gear member 20A.

The planetary gear set 22 includes a ring gear member 22A, a planetcarrier member 22B that rotatably supports a set of planet or piniongears 22D and a sun gear member 22C. The ring gear member 22A isconnected for common rotation with a fifth shaft or intermediate member50. The planet carrier member 22B is connected for common rotation witha sixth shaft or intermediate member 52. The sun gear member 22C isconnected for common rotation with the fourth shaft or intermediatemember 48 and a seventh shaft or intermediate member 54. Each of thepinion gears 22D are configured to intermesh with both the sun gearmember 22C and the ring gear member 22A.

The planetary gear set 24 includes a ring gear member 24A, a planetcarrier member 24B that rotatably supports a set of planet or piniongears 24D and a sun gear member 24C. The ring gear member 24A isconnected for common rotation with the sixth shaft or intermediatemember 52. The planet carrier member 24B is connected for commonrotation with the output shaft or member 16. The sun gear member 24C isconnected for common rotation with an eighth shaft or intermediatemember 56. Each of the pinion gears 24D are configured to intermesh withboth the sun gear member 24C and the ring gear member 24A.

The planetary gear set 26 includes a ring gear member 26A, a carriermember 26B that rotatably supports a set of planet or pinion gears 26Dand a sun gear member 26C. The ring gear member 26A is connected forcommon rotation with a ninth shaft or intermediate member 58. The planetcarrier member 26B is connected for common rotation with the outputshaft or member 16. The sun gear member 26C is connected for commonrotation with a first shaft or intermediate member 42. Each of thepinion gears 26D are configured to intermesh with both the sun gearmember 26C and the ring gear member 26A.

The transmission 10 also includes a plurality of torque-transmittingmechanisms or devices including a first clutch 66, a second clutch 68, athird clutch 70, a first brake 72 and a second brake 74. The firstclutch 66 is selectively engagable to connect the third shaft orintermediate member 46 to the eighth shaft or intermediate member 56.The second clutch 68 is selectively engagable to connect the secondshaft or intermediate member 44 to the eighth shaft or intermediatemember 56. The third clutch 70 is selectively engagable to connect theeighth shaft or intermediate member 56 to the ninth shaft orintermediate member 58. The first brake 72 is selectively engagable toconnect the seventh shaft or intermediate member 54 to the transmissionhousing 12 through a tenth shaft or member 60 to restrict rotation ofthe member 54 relative to the transmission housing 12. Finally, thesecond brake 74 is selectively engagable to connect the fifth shaft orintermediate member 50 to the transmission housing 12 through aneleventh shaft or member 62 to restrict rotation of the member 50relative to the transmission housing 12.

The transmission 10 is capable of transmitting torque from the inputshaft or member 14 to the output shaft or member 16 in at least eightforward torque ratios and one reverse torque ratio. Each of the forwardtorque ratios and the reverse torque ratio are attained by engagement ofone or more of the torque-transmitting mechanisms (i.e. first clutch 66,second clutch 68, third clutch 70, first brake 72 and second brake 74).Those skilled in the art will readily understand that a different speedratio is associated with each torque ratio. Thus, eight forward speedratios may be attained by the transmission 10.

The transmission housing 12 includes a first wall or structural member102, a second wall or structural member 104 and a third wall orstructural member 106. The third wall 106 interconnects the first andsecond walls 102 and 104 to define a space or cavity 110. Input andoutput shafts or members 14, 16 are supported by the second wall 104 bybearings 112 and bearings 114, respectively. The planetary gear sets 20,22, 24 and 26 and the torque-transmitting mechanisms 66, 68, 70, 72 and74 are disposed within cavity 110. Further, the cavity 110 has aplurality of areas or zones A, B, C, D, E, and F in which the pluralityof torque transmitting mechanisms 66, 68, 70, 72 and 74 will bespecifically positioned or mounted, in accordance with the preferredembodiments of the present invention.

As shown in FIG. 1A, zone A is defined by the area or space bounded by:the first wall 102, planetary gear set 22, radially inward by areference line “L” which is a longitudinal line that is axially alignedwith the input shaft 14, and radially outward by a reference line “M”which is a longitudinal line that extends adjacent an outer diameter orouter periphery of the planetary gear sets 20, 22, 24 and 26. Whilereference line “M” is illustrated as a straight line throughout theseveral views, it should be appreciated that reference line “M” followsthe outer periphery of the planetary gear sets 20, 22, 24 and 26, andaccordingly may be stepped or non-linear depending on the location ofthe outer periphery of each of the planetary gear sets 20, 22, 24 and26. Zone B is defined by the area bounded by: planetary gear set 22, theplanetary gear set 24, radially outward by reference line “M”, andradially inward by reference line “L”. Zone C is defined by the areabounded by: the planetary gear set 24, the planetary gear set 20,radially outward by reference line “M”, and radially inward by referenceline “L”. Zone D is defined by the area bounded by: the planetary gearset 20, the planetary gear set 26, radially outward by reference line“M”, and radially inward by reference line “L”. Zone E is defined by thearea bounded by: the planetary gear set 26, the second wall 104,radially outward by reference line “M”, and radially inward by referenceline “L”. Zone F is defined by the area bounded by: the first wall 102,the second wall 104, radially inward by reference line “M” and radiallyoutward by the third wall 106.

In the gear arrangement 18 of transmission 10 shown in FIG. 1A, theplanetary gear set 22 is disposed closest to the first wall 102, theplanetary gear set 26 is disposed closest to the second wall 104, theplanetary gear set 24 is disposed adjacent the planetary gear set 22,and the planetary gear set 20 is disposed between the planetary gearsets 24 and 26. The torque-transmitting mechanisms are intentionallylocated within specific Zones in order to provide advantages in overalltransmission size, packaging efficiency, and reduced manufacturingcomplexity. In the particular example shown in FIG. 1A, the first clutch66 and second clutch 68 are disposed within Zone C, the third clutch 70is disposed within Zone F and the first and second brakes 72 and 74 aredisposed within Zone A.

However, the present invention contemplates other embodiments where thetorque-transmitting mechanisms 66, 68, 70, 72 and 74 are disposed in theother Zones. The feasible locations of the torque-transmittingmechanisms 66, 68, 70, 72 and 74 within the Zones are illustrated in thechart shown in FIG. 1B. The chart of FIG. 1B lists clutches and brakesin the left most column and the available zones to locate theclutch/brake in the top row. An “X” in the chart indicates that thepresent invention contemplates locating the clutch or brake in the zonelisted in the top row. For example, first brake 72 may be located inzones A, B or F and second brake 74 may be located in zones A, B, C orF.

Referring now to FIG. 2, a front wheel drive powertrain 150incorporating a transaxle 153 is illustrated, in accordance with theembodiments of the present invention. Transaxle 153 includes thetransmission 10 having the gear arrangement 18 of FIGS. 1A and 1B.Transmission 10 is mounted to an engine 152. Engine 152 provides adriving torque through input shaft 14 to transmission 10. Engine 152 isgenerally an internal combustion engine, however, the present inventioncontemplates other types of engines such as electric and hybrid engines.Further, transaxle 153 includes a transfer gear train 154, adifferential 156, and a pair of drive axles 158 and 160 that drive apair of road wheels 162 and 164, respectively.

Transfer gear train 154 includes a first transfer gear 166 and a secondtransfer gear 168. Output shaft or member 16 is coupled to a firsttransfer or spur gear 166. First transfer gear 166 may be a straightspur gear having straight gear teeth or a helical gear having helicalgear teeth. First transfer gear 166 meshes with the second transfer gear168. Second transfer gear 168 is rotatably fixed to an intermediateshaft or rotatable member 170. Further, a pinion 172 is mounted to shaft170 and intermeshes with an input differential gear 174. Inputdifferential gear 174 is fixed to or integrally formed with the housingof the differential 156. Input differential gear 174 transfers drivingtorque to the differential 156. Differential 156, as conventionallyknown, transfers the driving torque generated by engine 152 to the twodrive axles 158 and 160. Drive axles 158 and 160 are independentlydriven by differential 156 to supply the driving torque to the vehicleroad wheels 162 and 164.

Referring now to FIG. 3, another embodiment of a front wheel drivepowertrain 200 incorporating a transaxle 202 is illustrated, inaccordance with the embodiments of the present invention. Transaxle 202includes the gear arrangement 18 of transmission 10 of FIGS. 1A and 1Band is mounted to the engine 152. Engine 152 provides a driving torquethrough input shaft 14 to transmission gear arrangement 10. Further,transaxle 202 includes a transfer chain 204, a driven sprocket or gear206, a differential 208, a final drive planetary gear set 210 and a pairof drive axles 158 and 160 that drive a pair of road wheels 162 and 164,respectively.

Transfer chain 204 engages, at a first end 212, a drive sprocket ortransfer gear 214 and at a second end 216 the driven sprocket ortransfer gear 206. The drive sprocket 214 is coupled to output shaft ormember 16. Driven sprocket 206 is rotatably fixed to a final drivemember or rotatable shaft 220. In an embodiment of the presentinvention, shaft 220 is a sleeve shaft through which drive axle 158passes. Further, shaft 220 is coupled to the sun gear of final driveplanetary gear set 210 to achieve the desired gear ratio. A carriermember of the final drive planetary gear set 210 supports a plurality ofpinion gears which mesh with both the sun gear and a ring gear of finaldrive planetary gear set. The carrier member of final drive planetarygear set 210 is rotatably coupled to and transfers driving torque to ahousing of the differential 208. Differential 208 transfers the drivingtorque generated by engine 152 to the two drive axles 158 and 160through two sets of bevel gears rotationally supported in thedifferential housing. Drive axles 158 and 160 are independently drivenby differential 208 to supply the driving torque to the vehicle roadwheels 162 and 164.

The description of the invention is merely exemplary in nature andvariations that do not depart from the gist of the invention areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theinvention.

1. A transaxle comprising: a transmission input member; a transmission output member; a housing having a first wall, a second wall, and a third wall extending between the first and second walls; a first, second, third and fourth planetary gear sets disposed within the housing, wherein the second planetary gear set is adjacent the first wall, the fourth planetary gear set is adjacent second wall, the third planetary gear set is adjacent the second planetary gear set and the first planetary gear set is between the third and fourth planetary gear sets, each planetary gear set having a sun gear member, a ring gear member, and a planet carrier member supporting a plurality of planet gears each configured to intermesh with both the sun gear member and the ring gear member, and wherein the ring gear member of the first planetary gear set is permanently coupled to the sun gear member of the fourth planetary gear set, the sun gear member of the first planetary gear set is permanently coupled to the sun gear member of the second planetary gear set, the planet carrier member of the second planetary gear set is permanently coupled to the ring gear member of the third planetary gear set, the planet carrier member of the third planetary gear set is permanently coupled to the planet carrier member of the fourth planetary gear set, the transmission output member is permanently coupled with the carrier members of the third and fourth planetary gear sets, and the transmission input member is permanently coupled with the carrier member of the first planetary gear set, and wherein the housing has a first area defined radially inward from an outer periphery of the planetary gear sets and axially bounded by the first wall and the second planetary gear set, a second area defined radially inward from the outer periphery of the planetary gear sets and axially bounded by the second and third planetary gear sets, a third area defined radially inward from the outer periphery of the planetary gear sets and axially bounded by the first and third planetary gear sets, a fourth area defined radially inward from the outer periphery of the planetary gear sets and axially bounded by the first and fourth planetary gear set, a fifth area defined radially inward from the outer periphery of the planetary gear sets and axially bounded by the fourth planetary gear set and the second wall, and a sixth area defined radially inward from the third wall and radially outward from the outer periphery of the planetary gear sets and axially bounded by the first wall and the second wall; a first clutch disposed in at least one of the second, third, fourth and sixth areas; a second clutch disposed in at least one of the third, fourth, fifth and sixth areas; a third clutch disposed in at least one of the third, fourth, fifth and sixth areas; a first brake disposed in at least one of the first, second and sixth areas; a second brake disposed in at least one of the first, second, third and sixth areas, and wherein the clutches and the brakes are selectively engageable to establish at least eight forward speed ratios and at least one reverse speed ratio between the transmission input member and the transmission output member; a transfer gear train having a first and second transfer gear, wherein the first transfer gear is rotatably fixed to the transmission output member and the second transfer gear is rotatably fixed to an intermediate shaft; a differential gear set for driving a pair of road wheels; a pinion gear rotatably fixed to the intermediate shaft; and an input differential gear in mesh with the pinion gear and configured to rotatably drive the differential gear set.
 2. The transaxle of claim 1 wherein the first clutch is selectively engageable to interconnect the planet carrier member of the first planetary gear set with the sun gear member of the third planetary gear set and is disposed in the third area, the second clutch is disposed in the third area, the third clutch is disposed in the sixth area, the first brake is disposed in the first area and the second brake is disposed in the first area.
 3. The transaxle of claim 1 wherein the first clutch is disposed within the second area.
 4. The transaxle of claim 1 wherein the first clutch is disposed within the fourth area.
 5. The transaxle of claim 1 wherein the first clutch is disposed within the sixth area.
 6. The transaxle of claim 1 wherein the second clutch is selectively engageable to interconnect the ring gear member of the first planetary gear set with the sun gear member of the third planetary gear set wherein the second clutch is disposed within the third area.
 7. The transaxle of claim 1 wherein the second clutch is disposed within the fourth area.
 8. The transaxle of claim 1 wherein the second clutch is disposed within the fifth area.
 9. The transaxle of claim 1 wherein the second clutch is disposed within the sixth area.
 10. The transaxle of claim 1 wherein the third clutch is selectively engageable to interconnect the ring gear member of the fourth planetary gear set with the sun gear member of the third planetary gear set and wherein the third clutch is disposed within the sixth area.
 11. The transaxle of claim 1 wherein the third clutch is disposed within the third area.
 12. The transaxle of claim 1 wherein the third clutch is disposed within the fourth area.
 13. The transaxle of claim 1 wherein the third clutch is disposed within the fifth area.
 14. The transaxle of claim 1 wherein the first brake is selectively engageable to interconnect the sun gear member of the second planetary gear set to the housing and wherein the first brake is disposed within the first area.
 15. The transaxle of claim 1 wherein the first brake is disposed within the second area.
 16. The transaxle of claim 1 wherein the first brake is disposed within the sixth area.
 17. The transaxle of claim 1 wherein the second brake is selectively engageable to interconnect the ring gear member of the second planetary gear set to the housing and wherein the brake is disposed within the first area.
 18. The transaxle of claim 1 wherein the second brake is disposed within the second area.
 19. The transaxle of claim 1 wherein the second brake is disposed within the third area.
 20. The transaxle of claim 1 wherein the second brake is disposed within the sixth area.
 21. A transaxle comprising: a transmission input member; a transmission output member; a housing having a first wall, a second wall, and a third wall extending between the first and second walls; a first, second, third and fourth planetary gear sets disposed within the housing, wherein the second planetary gear set is adjacent the first wall, the fourth planetary gear set is adjacent second wall, the third planetary gear set is adjacent the second planetary gear set and the first planetary gear set is between the third and fourth planetary gear sets, each planetary gear set having a sun gear member, a ring gear member, and a planet carrier member supporting a plurality of planet gears each configured to intermesh with both the sun gear member and the ring gear member, and wherein the ring gear member of the first planetary gear set is permanently coupled to the sun gear member of the fourth planetary gear set, the sun gear member of the first planetary gear set is permanently coupled to the sun gear member of the second planetary gear set, the planet carrier member of the second planetary gear set is permanently coupled to the ring gear member of the third planetary gear set, the planet carrier member of the third planetary gear set is permanently coupled to the planet carrier member of the fourth planetary gear set, the transmission output member is permanently coupled with the carrier members of the third and fourth planetary gear sets, and the transmission input member is permanently coupled with the carrier member of the first planetary gear set, and wherein the housing has a first area defined radially inward from an outer periphery of the planetary gear sets and axially bounded by the first wall and the second planetary gear set, a second area defined radially inward from the outer periphery of the planetary gear sets and axially bounded by the second and third planetary gear sets, a third area defined radially inward from the outer periphery of the planetary gear sets and axially bounded by the first and third planetary gear sets, a fourth area defined radially inward from the outer periphery of the planetary gear sets and axially bounded by the first and fourth planetary gear set, a fifth area defined radially inward from the outer periphery of the planetary gear sets and axially bounded by the fourth planetary gear set and the second wall, and a sixth area defined radially inward from the third wall and radially outward from the outer periphery of the planetary gear sets and axially bounded by the first wall and the second wall; a first clutch disposed in at least one of the second, third, fourth and sixth areas and is selectively engageable to interconnect the planet carrier member of the first planetary gear set with the sun gear member of the third planetary gear set; a second clutch disposed in at least one of the third, fourth, fifth and sixth areas and is selectively engageable to interconnect the ring gear member of the first planetary gear set with the sun gear member of the third planetary gear set; a third clutch disposed in at least one of the third, fourth, fifth and sixth areas and is selectively engageable to interconnect the ring gear member of the fourth planetary gear set with the sun gear member of the third planetary gear set; a first brake disposed in at least one of the first, second and sixth areas and is selectively engageable to interconnect the sun gear member of the second planetary gear set to the housing; a second brake disposed in at least one of the first, second, third and sixth areas and is selectively engageable to interconnect the ring gear member of the second planetary gear set to the housing, and wherein the clutches and the brakes are selectively engageable to establish at least eight forward speed ratios and at least one reverse speed ratio between the transmission input member and the transmission output member; a power transfer assembly having a first and a second transfer gear and a power transfer member, wherein the first transfer gear is rotatably fixed to the transmission output member and the second transfer gear is rotatably fixed to a final drive member and wherein the power transfer member rotatably couples the first and second transfer gears for transferring rotational energy from the first transfer gear to the second transfer gear; a final drive planetary gear set having a final drive sun gear coupled to the final drive member, a final drive ring gear coupled to the transmission housing and a final drive carrier member rotatably supporting a final drive plurality of pinion gears intermeshed with both the final drive sun gear and the final drive ring gear; and a differential gear set having a differential housing coupled to the final drive carrier member and having a pair of gears rotatably supported in the differential housing, wherein one of the pair of the gears is rotatably fixed to one of a pair of road wheels and the other of the pair of the gears is rotatably fixed to the other one of the pair of road wheels.
 22. The transaxle of claim 21, wherein the power transfer member is a chain or a belt. 